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Control linkages and hydraulics question


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...and you stop moving the cyclic when you achieve that angle of bank, the autopilot will attempt to, within its 20% authority, hold that 10 degree angle of bank, with the cyclic still being deflected to the left. With the autopilot off, you're now dealing with just the standard aerodynamics. I believe on the Mi-8 it will tend to roll out of shallow banks by itself. That is, for shallow banks, you may need to keep the cyclic deflected or else it will just naturally roll back to level. Then at some intermediate angles of bank, it will naturally hold that bank angle and the cyclic would be returned to center (or very nearly center) and the bank angle will just sort of hold itself. And then beyond some intermediate bank angle you will get the overbanking tendency, where the aircraft will tend to bank even more and you will have to apply slight opposite cyclic (opposite side of being centered) to keep the bank from continuing to exaggerate. I do not know what the angles involved are, but if memory serves (and it probably doesn't), an shallow bank angle is 15 degrees or less, intermediate is from maybe 15-40 degrees, and beyond 40 degrees you'll get overbanking tendency. I could be very wrong on those so as soon as someone argues with me I'll just edit this post and delete it. :D

 

I could be thinking of the over and underbanking tendencies in my Cessna.

 

 

We had another thread going about cyclic position during a sustained turn.

( https://forums.eagle.ru/showthread.php?t=231698

 

It wasn't about the mi-8, but basic principles of flight and somehow the mi-8 entered the discussion. To sum it up, this discussion was basic helicopter without AP, and the conclusion is that all helos will have the cyclic close to center latterally in a turn and this have to be the same for the mi-8, at least with AP of. I found support for this in the flight manual, and also in some flight tests, where the lateral stick position was logged.

 

Basically, we know that the mi-8 need stick input around center, often opposite lateral during turn(as with lot of helos and aircrafts) and the question from the OP i think was related to the fact that in DCS mi-8 with AP of, stick is around center in a turn but when AP on, you need to keep it deflected. The OP question was about hydraulics and mechanical link from stick to swash, trying to find a reason why the module changes behavior with AP on/off.

 

The other thread had a long way to come to the conclusion that stick around center for a continuous banked turn is valid for virtually all helicopters( and aircrafts), I suggest reading this if the stick@center in turns isn't clear.

[T.M HOTAS Warthog Stick & Throttle + T.Flight pedals, Varjo Aero, HP Reverb pro, Pimax 8KX] 🙂

[DCS Mirage 2K; Huey; Spitfire Mk IX, AJS 37, F-14, F-18, FC3, A-10 Warthog II and a few more ]

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verifying the behavior of the DCS Mi-8 to be correct

 

From the explanation it does seem so. I've got to do some flight tests when I get off work today and really pay attention to how the stab system works and what are the control differences with it on and off.

The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.

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Bonjour gents and gentettes. The Mi-17 Dash-10 manual states that:

 

 

 

But what does this mean exactly? Are there two separate systems for redundancy, one mechanical and the other hydraulic? Or does it mean that the control rods are connected to the servos/actuators and never interact with the swashplate directly?

 

 

It means that there is mechanical system from cabin controls through force feedback spring mechanism and trim to hydraulic actuators. Hydraulic actuators are connected to swashplate and ropes for controlling tail rotor. So there is no redundant systems. Only mechanical conected to hydro actuators conected to swashplate and tail rotor control.

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Yeah, that much is clear already, but thanks anyway.

 

Just found a very nice writeup and description with pictures from A16:

https://forums.eagle.ru/showthread.php?t=110313

 

Quite easy to the that the control rods are mechanichally connected to the swash.

What we dont see is the 20% internal adjustment the autopilot can do. Either use the link below togheter with google.translate, or just believe it anyway :)

 

http://cnit.ssau.ru/vertolet/mi8/

[T.M HOTAS Warthog Stick & Throttle + T.Flight pedals, Varjo Aero, HP Reverb pro, Pimax 8KX] 🙂

[DCS Mirage 2K; Huey; Spitfire Mk IX, AJS 37, F-14, F-18, FC3, A-10 Warthog II and a few more ]

i9 13900KF@5.8/32Gb DDR5@6400/ Gigabyte Gaming OC RTX4090, ASUS STRIX Z790-F , 2Tb m2 NVMe

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  • 1 month later...

Just wondering if there has been a resolve for this, without the autopilot the Mi-8 has the same feel as Huey and gazelle in response to cyclic input.

 

If not I guess we should raise a bug report given the two different cyclic actions with and without autopilot.

Control is an illusion which usually shatters at the least expected moment.

Gazelle Mini-gun version is endorphins with rotors. See above.

 

Currently rolling with a Asus Z390 Prime, 9600K, 32GB RAM, SSD, 2080Ti and Windows 10Pro, Rift CV1. bu0836x and Scratch Built Pedals, Collective and Cyclic.

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  • 3 weeks later...
The autopilot will attempt to hold the pitch and bank angles if the cyclic is not moving. That is, if the cyclic is stationary, the pitch and roll channels of the autopilot will attempt to hold the pitch and bank attitudes within its 20% authority.

 

If the cyclic is moving the autopilot still tries to hold the attitude, but essentially it's holding the attitude around a moving target, since the movement of the cyclic is being removed from the equation.

 

This is why it's more similar to a SAS-type system than what most people would consider a traditional "autopilot".

 

And so it follows that if you, for example, move the cyclic to the left to enter a 10 degree angle of bank, and you stop moving the cyclic when you achieve that angle of bank, the autopilot will attempt to, within its 20% authority, hold that 10 degree angle of bank, with the cyclic still being deflected to the left. With the autopilot off, you're now dealing with just the standard aerodynamics. I believe on the Mi-8 it will tend to roll out of shallow banks by itself. That is, for shallow banks, you may need to keep the cyclic deflected or else it will just naturally roll back to level. Then at some intermediate angles of bank, it will naturally hold that bank angle and the cyclic would be returned to center (or very nearly center) and the bank angle will just sort of hold itself. And then beyond some intermediate bank angle you will get the overbanking tendency, where the aircraft will tend to bank even more and you will have to apply slight opposite cyclic (opposite side of being centered) to keep the bank from continuing to exaggerate. I do not know what the angles involved are, but if memory serves (and it probably doesn't), an shallow bank angle is 15 degrees or less, intermediate is from maybe 15-40 degrees, and beyond 40 degrees you'll get overbanking tendency. I could be very wrong on those so as soon as someone argues with me I'll just edit this post and delete it. :D

 

I could be thinking of the over and underbanking tendencies in my Cessna.

 

EDIT: I asked one of our pilots about it and he said, basically, "Heck I don't know, I just do whatever makes it point where I want it to point." SO in other words he doesn't think about it enough to answer offhand.

 

Thanks however, respectfully there is no actual definitive answer for the cyclic behaviour with AP on.

 

FWIW With AP off the Mi-8 handles much like the Huey and Gazelle does in regard to cyclic deflection verse rate of roll. Interesting. :)

Control is an illusion which usually shatters at the least expected moment.

Gazelle Mini-gun version is endorphins with rotors. See above.

 

Currently rolling with a Asus Z390 Prime, 9600K, 32GB RAM, SSD, 2080Ti and Windows 10Pro, Rift CV1. bu0836x and Scratch Built Pedals, Collective and Cyclic.

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The current behavior is correct.

 

Okay thanks I'll stick to turning AP off in that case, it actually "feels" better to fly it that way. :thumbup:

Control is an illusion which usually shatters at the least expected moment.

Gazelle Mini-gun version is endorphins with rotors. See above.

 

Currently rolling with a Asus Z390 Prime, 9600K, 32GB RAM, SSD, 2080Ti and Windows 10Pro, Rift CV1. bu0836x and Scratch Built Pedals, Collective and Cyclic.

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it actually "feels" better to fly it that way

 

Well tastes differ but this I don't get. The Huey's twitchy, as the real thing seems to be too, but this thing here is a f**n truck and you'll want ALL the stability you can get (or I do at any rate). So why the hell switch _any_ of the RL stabs off? Da mind buggles :D

The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.

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Well tastes differ but this I don't get. The Huey's twitchy, as the real thing seems to be too, but this thing here is a f**n truck and you'll want ALL the stability you can get (or I do at any rate). So why the hell switch _any_ of the RL stabs off? Da mind buggles :D

 

That's interesting I don't find the Huey twitchy in the slightest or even the the Gazelle granted the Gazelle's cyclic is sensitive and it is lighter and all as well.

 

For me the Mi-8 with AP off feels fine, actually natural and I think I have any problems manoeuvring that puppy with AP off, it's responsive given it's mass and it can be a ton of fun (pun intended) throwing it around between trees, buildings and those pesky power lines at a few meters above the ground. :D

 

You know you can get the mast pointing to the ground pretty much inverted and survive,... :thumbup:

 

The BO-105 should be interesting,.. I do like Chuck Aaron's instructional videos. :helpsmilie: :music_whistling:

Control is an illusion which usually shatters at the least expected moment.

Gazelle Mini-gun version is endorphins with rotors. See above.

 

Currently rolling with a Asus Z390 Prime, 9600K, 32GB RAM, SSD, 2080Ti and Windows 10Pro, Rift CV1. bu0836x and Scratch Built Pedals, Collective and Cyclic.

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So that's it from the horse's mouth so to speak. :thumbup:

 

To be clear here I said I appreciated the response but hell I like facts you know those things that are provable, not opinion based. That's the way I roll. :)

Control is an illusion which usually shatters at the least expected moment.

Gazelle Mini-gun version is endorphins with rotors. See above.

 

Currently rolling with a Asus Z390 Prime, 9600K, 32GB RAM, SSD, 2080Ti and Windows 10Pro, Rift CV1. bu0836x and Scratch Built Pedals, Collective and Cyclic.

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